The invention relates to swirler assemblies for supplying compressed air to the combustor of gas turbine engines.
A gas turbine engine includes a compressor that provides pressurized air to a combustor wherein the air is mixed with fuel and ignited for generating hot combustion gases. These gases flow downstream to one or more turbines that extract energy therefrom to power the compressor and provide useful work such as powering an aircraft in flight. In combustors used with aircraft engines, the fuel is typically supplied to the combustor through a plurality of fuel nozzles positioned at one end of the combustion zone. The air is supplied through surrounding assemblies, known as swirler assemblies, which impart a swirling motion to the air so as to cause the air and fuel to be thoroughly mixed. The swirler assemblies are mounted in a dome plate that is joined to the upstream ends of the combustor's inner and outer liners, and each fuel nozzle tip is received in a corresponding one of the swirler assemblies.
One conventional swirler assembly is a three part assembly comprising a primary swirler, a secondary swirler and a retainer. The primary swirler has a plurality of circumferentially spaced swirl vanes or air passages. The vanes or passages are angled with respect to the axial centerline of the swirler assembly so as to impart a swirling motion to the air flow. The secondary swirler, also having a plurality of circumferentially spaced swirl vanes or air passages, is disposed immediately downstream of the primary swirler. The vanes or passages of the secondary swirler are angled so as to produce a swirl of air swirling in the opposite direction as the primary swirler to further promote fuel-air mixing. The retainer fits over the primary swirler and is welded to the secondary swirler to retain the two swirlers in engagement with one another.
The air flow through the vanes or passages of the primary swirler creates a reaction force that tends to cause the primary swirler to rotate with respect to the secondary swirler and the fuel nozzle. However, if allowed to rotate, the primary swirler would fail to impart the necessary level of swirling to the air, and effective mixing of the air and fuel would not be achieved. Furthermore, rotation of the primary swirler would cause excessive wear to the fuel nozzle tip. Primary swirler rotation is thus prevented in conventional swirler assemblies by providing an outwardly extending tab on the primary swirler and a post on the secondary swirler, wherein the tab engages the post so as to limit relative rotation of the swirlers.
However, the combustor structure is vibrationally active and there is substantial thermal expansion of components during operation of a gas turbine engine. As a result, there is relative movement between the tab and the post resulting in significant wear that eventually requires repair and increases maintenance costs. The repair process is relatively difficult because it requires removal of the permanently welded retainer. It is also possible that a worn tab and/or post could break off and cause damage to the turbine downstream. Furthermore, the retainer is susceptible to cracking during operation and often needs to be replaced.
Accordingly, there is a need for an improved swirler assembly that can prevent and preferably prevent rotation of the primary swirler relative to the secondary swirler, to eliminate frequent repairs, and which is easy to field assemble and disassemble.